1. Field of the Invention
The present invention relates to a head pad made so as to bring a flexible magnetic sheet-like disk able to be used for electronic still cameras, for example, into contact with a magnetic head by negative pressure and to a process for production of the same.
2. description of the Related Art
The recording format of an electronic still camera, for example, is of a short wavelength, so to perform stable magnetic recording or reproduction by a magnetic head, the magnetic head is projected out at the center of a pad (negative pressure type pad) and the flexible magnetic sheet-like disk is rotated while being drawn by to the pad by negative pressure. Explaining this in more detail using FIGS. 1 to 4, reference numeral 1 is a disk-like pad. The top face o the pad 1 forms a drawing face 1a which draws to it a flexible magnetic sheet-like disk A by negative pressure. At the center is formed a rectangular aperture 1a. In the aperture 1b is fixed a magnetic head 2 by an adhesive 3 so as to project out several microns from the drawing face 1a.
The pad 1 with the magnetic head 2 projecting out is made reciprocatively movable in the radial direction of the disk A by a head feed device 4 of a disk drive device shown in FIG. 1. That is, the head feed device 4 substantially includes a head carriage 5 which holds the pad 1, a pair of slide shafts 8a and 8b which are disposed in parallel at a predetermined distance at a top chassis 6a and guide the head carriage 5 to a turntable 7 side of a spindle motor, and a large diameter gear 10 which engages with a small diameter gear 9a of a motor 9 affixed to a bottom chassis 6a, has at its top face a screw-like cam 10a which engages with a pin-shaped cam follower 5a projecting from the bottom face of the head carriage 5, and reciprocatively moves the had carriage 5 in a straight line.
When a disk A is held and rotated at the turntable 7 of the spindle motor, the negative pressure of the air flow created between the disk A and the drawing face 1a of the pad 1 due to the rotation of the disk A (pressure lower than surrounding atmospheric pressure using vicinity of air flow) causes the disk A to turn while being drawn to the drawing face 1a of the pad 1 and thus enabling stable contact to the magnetic head 2.
However, differences in the precision of the flatness of the drawing face 1aof the pad 1 easily result in variations in the negative pressure created between the drawing face 1a and the disk A and therefore there was the problem that a stable head touch could not be obtained at all times.
Further, differences in the state of undulation (flatness) of the disk A during rotation means that the negative pressure fluctuated tremendously, resulting in the disk A being weakly drawn to the magnetic head 2 as shown by the solid line in FIG. 4 or the disk A being strongly drawn to the magnetic head 2 as shown by the dot-chain line, so there was the problem that the spacing loss between the magnetic disk 2 and the disk A ended up increasing and the head touch deteriorated. As a result, it was not possible to stably record/reproduce short wavelengths in the recording format of the electronic still camera.
The assignee disclosed in Japanese Unexamined Patent Application Publication No. 1-315061 the constitution of a head pad which could stably generate negative pressure and improve the head touch by a simple structure. Explaining this using FIG. 5 and FIG. 6 giving the same reference numerals to portions substantially the same as in the construction of the prior art, two annular depressions 1c, 1c having depressions of, for example, 50 to 20 microns, are formed by cutting inside an outside at the peripheral portion of the magnetic head 2 on the drawing face 1a of the pad 1 so as to leave a rib on the drawing face 1a.
If a disk A is inserted to the turntable 7 of the spindle motor in the disk drive device of an electronic still camera using this pad 1 and the disk A is rotated at a high speed by the motor drive of the spindle motor, then the air pressure between the two depressions 1a, 1c of the drawing face 1a of the pad 1 and the disk A will become negative pressure, the disk A will be drawn to the pad 1 side, and the disk A will contact the magnetic head 2 projecting form the pad 1 with a constant contact pressure. At this time, since two depressions 1c, 1c are formed inside and outside around the magnetic head 2 of the drawing face 1a of the pad 1, it is possible to reduce to a indium the variation of the negative pressure occurring between the depressions 1c of the drawing face 1a of the pad 1 and the disk A, regardless of the difference in precision of the flatness of the drawing face 1a of the pad 1 and the undulation etc. of the disk A during rotation and it is possible to increase the drawing force of the magnetic head 2 by the pad 1 to more than in the pad and thus obtain stable contact.
With a pad 1 having so depressions 1c, 1c formed inside and outside around the magnetic head 2 on the drawing face 1a of the above related art, the depressions 1c, 1c enabled negative pressure to be obtained, but the inner circumferential face and outer circumferential face of the portions forming the rib formed between the depressions 1c, 1c (shown by reference numeral 1d in FIG. 6) stood at right angles to the bottom face of the depressions 1c, 1c, so in some cases sufficient negative pressure could not be obtained due to the differences in the machining precision etc. of the components.
Further, securing the surface precision and dimensional precision required in producing the drawing face 1a and the depressions 1c of the pad 1 required rough inspection and quality control. Also, it was difficult and costly to mass produce these with a high precision.